Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Another windy, snowy storm will impact the Cascades Tuesday night. Strong winds will build stiff unstable slabs of snow at all elevations. To avoid triggering or being caught in an avalanche, travel on low angle slopes and avoid deep pillow-like drifts on steep terrain features. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Areas near the Cascade Crest, such as Salmon La Sac, Trinity, and Holden, could end up with around 8-10inches of new snow. Expect smaller snow totals in areas further east, such as Mission Ridge or the Entiat. With very strong winds in the forecast, it may be hard to find locations where the wind hasn't drifted the snow around. While these wind slabs may be smaller at lower elevations, they will quickly gain size as you ascend in elevation to more exposed terrain. You should also anticipate that these slabs may form further down from ridges than you would typically see or in areas you would usually consider sheltered. In many locations, these new slabs will rest on a freezing rain or sleet crust from Christmas, and there is uncertainty about how well the new snow will bond to this slippery underlying surface. Sensitive, fresh wind slabs and slick, old snow surfaces are a perfect setup for avalanches. Wednesday will be a good day to stick to low angle slopes in sheltered areas. You can identify wind-affected terrain by surface texturing, shooting cracks, and stiff hollow sounding snow. If you observe any of these signs, steer clear of steep terrain. 

    (12/5/2021)

    Wind rippled snow in south-facing terrain near a pass east of Grindstone Mountain in the East Central Zone.

    Photo: Matt Primomo

Avalanche Discussion

We have been on a wild weather ride for the last few days, and Wednesday will be a continuation of that pattern. Times of rapidly changing and active weather limit the ability to gather information on a broad spatial scale throughout the area. Since we have limited information, we also have significant uncertainty about snowpack conditions. We suspect many areas have a widespread ice crust from the freezing rain/sleet over the Christmas weekend. This crust may never have formed at higher elevations, and you may find a melt-freeze crust from rain instead. At trailheads at the lowest elevations, the freezing rain crust may have broken down with the recent warm temps, and you may find a saturated snowpack.

With this complicated snowpack setup, you may find a complex set of avalanche problems. While wind slabs are the primary concern, low elevations may still present some wet avalanche concerns. Temperatures are dropping and will help to freeze the wet mushy snow, but at low elevations, wet loose slides or larger, more dangerous wet slab avalanches may still be something to consider. On Tuesday near Mission Ridge, an NWAC forecaster observed some small wet slabs on steep cut banks. Look for signs such as roller balls or heavy saturated snow to indicate the potential for wet loose or wet slab avalanches. At higher elevations, new snow falling on slick crusts could form storm slabs in even sheltered locations. Use quick hand pits or inconsequential test slopes to see how well the new snow bonds with the underlying surfaces. 

If you take advantage of some time off work and get out into the mountains, help us out by sending in an observation!

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